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Graphene is an atomic-scale honeycomb lattice made of carbon atoms.

Image: Wikipedia

Issue no. 3, 2012 Published: Feb 03, 2012
Slow graphene down, speed computers up
Scientists decode how the brain hears words
First brain movie captures a mouse thinking
Spider silk's flexibility makes webs super-strong
Salmon storage: New memory device based on fish DNA
Parking sensors to take pain out of finding a space

Slow graphene down, speed computers up
Astonishing conductivity helped the discoverers of graphene win the Nobel prize in physics in 2010. Now a way to switch off the easy flow of electrons in this form of carbon is bringing superfast graphene computers closer. A sheet-like molecule just one carbon atom thick, graphene offers much less resistance to the flow of electrons than silicon. It has been hailed for its potential as the basis for computer circuits that operate at unprecedented speed. But the ease of electron flow also creates a problem. To perform calculations, computers need to turn the flow of electricity on and off in their circuits. The gates that open and close to regulate the flow are called transistors. Making graphene-based transistors has proven difficult because it is such a good conductor. Previous attempts have involved electrons confined to a single layer of graphene, but these still suffer from a leakage of electrons when the transistor is in its 'off' state. Now researchers at the University of Manchester have found a way to overcome this leakage problem by sandwiching a layer of molybdenum disulfide between two layers of graphene. The molybdenum acts as an insulator, preventing electrons from flowing in the normal way from one graphene layer to the other. This constitutes an 'off' state. A quantum mechanical effect means a small number of electrons can 'tunnel' through the molybdenum. This normally happens very rarely but applying a voltage across the barrier boosts the energy of the electrons, making tunnelling much more probable - a sizable current starts to flow. This is the 'on' state. By varying the voltage, the researchers could turn the flow on and off, making the device a transistor. The graphene sandwich reduces leakage by a factor of 10 compared with previous graphene-based transistors.
New Scientist / Science Feb 02, 2012	back to top

Scientists decode how the brain hears words
Scientists at the University of California, Berkeley, have found a way to decode how the brain hears words, in a major step toward one day helping people communicate after paralysis or stroke. By placing electrodes on the brains of research subjects and then having them listen to conversations, scientists were able to analyze the sound frequencies registered and figure out which words they were hearing. By tracking how and where the brain registered sounds in the temporal lobe - the centre of the auditory system - scientists were able to map out the words and then recreate them as heard by the brain. One word the researchers mapped was 'structure'. The high-frequency 's' sound showed up as a certain pattern in the brain, while the lower harmonics of the 'u' sound appeared as a different pattern. The work builds on previous research in ferrets, in which scientists read to the animals and recorded their brain activity. They were able to decode which words the creatures heard even though the ferrets themselves didn't understand the words. The next step for researchers is to figure out just how similar the process of hearing sounds may be to the process of imagining words and sounds. That information could one day help scientists determine what people want to say when they cannot physically speak.
Yahoo! / AFP / PLoS Biology Feb 01, 2012	back to top

First brain movie captures a mouse thinking
Ever wondered what is going on in the brain of a mouse? Now brain cells have been captured sending and receiving signals in high resolution for the first time, essentially showing its brain in action. To make the tiniest anatomical details of neurons visible, researchers at the Max Planck Institute for Biophysical Chemistry in Göttingen, Germany, gave mice an extra gene that generates a yellow glow. When their brains were viewed with a special microscope through a glass-sealed window in the skull, the signal junctions in neurons lit up. At these intersections, tiny spines sprout from longer branching fibres, called dendrites, and exchange signals by linking up with spines on neighbouring cells. The movie spans a 20 to 30 minute period, during which a live mouse was anaesthetised. The spines physically move and wobble at the top and base as they form and break connections with neighbouring spines. Brain cells have been imaged in live animals before, but the latest movie is the first to reveal parts of neurons in such fine detail - down to a resolution of 70 nanometres. According to the team, the breakthrough should enable researchers to investigate the faulty connectivity that arises in a mouse brain when it is affected with a version of a human disease, such as dementia. Although the current images show the surface of the cerebral cortex, an area of the brain that controls movement, the researchers claim that it may be possible to penetrate deeper. This would allow implants to be developed, enabling the spines to be viewed while the animal is conscious and mobile.
New Scientist / Science Feb 02, 2012	back to top

Spider silk's flexibility makes webs super-strong
A spider web's ability to adapt to different levels of stress is the key to its remarkable stability, say scientists at MIT. As well as seeing how much strain natural webs could take, researchers used computer simulations to find out how the silk structures responded. Webs stood up to a variety of stresses, including hurricane-force winds. They discovered that a spider web's design, and the unique properties of its silk, allowed just a single thread to break so the rest of the web remained unharmed. The team studied the webs of a variety of species including European garden spiders and orb weavers. By investigating the silk on a molecular scale, the researchers found they could explain the behaviour of the web as a whole. Each individual thread of silk could be 'sacrificed' to maintain the overall structure. The key to this ability lies in the fact that the silk 'changes' as it is tugged at. This change occurs in four stages: In the first phase the entire thread is pulled taught; it is then 'drawn out' and stretched as the proteins making up the thread 'unfold'. In the third stage, the thread goes through a 'stiffening phase' that absorbs the greatest amount of force. There is then one final phase just before the silk breaks, which the researchers call 'stick-slip'. They compare it to pulling on a piece of sticky tape in an effort to break it; a great force is needed to break the thread because the proteins are being held together by 'sticky' hydrogen bonds. The 'slipping and sticking' occurs because although the force breaks the bonds - some of them reform. This process repeats, with fewer and fewer of the bonds sticking back together, until none remain and the thread breaks completely.
BBC News / Nature Feb 01, 2012	back to top

Salmon storage: New memory device based on fish DNA
In order to find a method for more cost-effective data storage, a group of researchers at the Karlsruhe Institute of Technology (KIT) in Germany and the National Tsing Hua University in Taiwan have created a DNA-based 'write-once-read-many-times'(WORM) memory device. The device consists of a thin film of salmon DNA, which has been embedded with nano-sized particles of silver and then sandwiched between two electrodes. Ultraviolet light is used to encode information. Shining UV light on the system causes the silver atoms to cluster into nano-sized particles. These particles provide the platform for the data encoding. The device is able to hold charge under a low current, which corresponds to the off-state. Under a high electrical field the charges pass through the device, which then corresponds to the on-state. The team found that once the system had been turned on, it stayed on; changing the voltage across the electrodes did not change the system's conductivity. This means that information can be written to the device but not overwritten. Once written, the device appears to retain that information indefinitely. The material's conductivity did not change significantly during nearly 30 hours of tracking. The authors expect the technique to be useful in the design of optical storage devices and suggest that it may have plasmonic applications as well.
R&D Magazine / Applied Physics Letters Jan 31, 2012	back to top

Parking sensors to take pain out of finding a space
It's a problem familiar to most of us: you circle for ages waiting to find a parking space and just when you've spotted one, someone else darts in first. Now a 'parking patch' could change that by bringing together wireless sensors and mobile apps to steer drivers towards those elusive vacant spots, while also allowing traffic wardens to home in on parking offenders. Some local authorities have already started embedding radio frequency identification (RFID) tags in parking permits. But while this makes it easier for wardens to check their validity with a quick scan by a handheld reader, it does little else. The real challenge lies in telling when a parking space is empty or occupied without having to fit a car with any special equipment. A solution, developed by British start-up Deteq Solutions, is to attach cheap, low-powered wireless sensors to the road surface in each parking bay. These 7-centimetre-wide patches are glued down in the centre of each bay, where they can detect when a car is present or not. The device will wirelessly relay information to a base station via a mesh network with its neighbours. This means the system does not require any new infrastructure. It is designed to work in conjunction with RFID permits if required, and a smartphone app. The app would give drivers real-time information about available parking spaces near where they were, with streets colour-coded depending on how many spots were free at the time. The system can also alert traffic wardens when drivers have parked on no-stop zones, helping to reduce congestion. It could allow local authorities to use dynamic parking tariffs. This is where real-time data about the occupancy of spaces is used to set parking prices. So parking in less congested areas and at quieter times of day would be cheaper.
New Scientist Feb 01, 2012	back to top